How to connect the equipotential bonding in the HMI cabinet?

Achieving equipotential bonding within the HMI cabinet is crucial for ensuring stable system operation in electromagnetic interference environments. All metal components installed within the cabinet, such as the HMI unit itself, PLC, power modules, cable trays, cabinet doors, and mounting backplate, should be connected to the common grounding busbar or cabinet grounding point via low-impedance conductors. Connections should use dedicated grounding wires or braided tape with a cross-sectional area sufficient to handle potential fault currents. Paint or oxide layers should be removed from connection points, and toothed washers should be used to ensure good contact. The cabinet grounding busbar itself should be reliably connected to the building's grounding system. For the HMI unit, its metal casing should be electrically connected to the cabinet backplate via its built-in grounding terminal or mounting rails.

All cable shielding entering the cabinet should be connected to the cabinet grounding busbar at the entrance via shielding clips or grounding terminal blocks, achieving a 360-degree overlap. The equipotential bonding network should be star-shaped or mesh-like to avoid large grounding loops. In industrial environments where high-frequency interference may exist, the equipotential bonding network must consider high-frequency characteristics; flat braided tape or copper busbars are preferable to round wires. Good equipotential bonding ensures that all devices in the cabinet are at the same reference potential, reducing common-mode interference and ground loop problems caused by potential differences, and is the cornerstone of the field reliability of HMI systems.